random-line-access

random-line-access

Provides random access to keyed lines of arbitrarily sized files.

If you have a file larger than memory that you want to retrieve rows from at random, and your file happens to be structured such that the first word of each line can be regarded as a key for the entire line, well, then this is what you've been looking for.

Usage

example1,1,2,3,4
example2,hamburger,rango,,,martians
somemore,ozone,zone,zoneout
"wow complex",margarine,bananas,,,robot

const randomLineAccess = require('random-line-access')

let rla = randomLineAccess('huge.csv', {sep: ','})

rla.ls(function(err, ls) {
  console.log(ls) // ['example1', 'example2', 'somemore', '"wow']
})

rla.get('example2', function(err, data) {
  console.log(data) // ['hamburger', 'rango', 'martians']
})

let rla = randomLineAccess('huge.csv', {sep: ',', omitEmpty: false})
rla.get('example2', function(err, data) {
  console.log(data) // ['hamburger', 'rango', '', '', '', 'martians']
})


let rla = randomLineAccess('huge.csv')
rla.get('example1', function(err, data) {
  console.log(data) // '1,2,3,4'
})

let rla = randomLineAccess('huge.csv', {sep: ',', quotes: true})
rla.ls(function(err, ls) {
  console.log(ls) // ['example1', 'example2', 'somemore', 'wow complex']
})

rla.get('wow complex', function(err, data) {
  console.log(data) // ['margarine', 'bananas', 'robot']
})

rla.set('wow complex', ['molasses'], function(err, data) {
  console.log(data) // ['molasses']
})

rla.close()

API

randomLineAccess

• randomLineAccess(filePath, opts) Filepath to any file. Careful: the set operator has write permission Options include:
  • omitEmpty Expects a boolean, defaults to true. Removes empty values.
  • quotes Expects a boolean, defaults to false. Accepts quotes in the key value (IS IGNORED IN SEPARATED VALUES)
  • sep Expects a string. When provided, returns values seperated by the separator, and inserts arrays joined by seperator.

Instance

• get(key, callback) Takes a key and returns the value retrieved to the callback.

• set(key, buffer, callback) Careful: the set operator has write permission, and no undo Takes a key, and either a buffer or a string. If the resulting buffer from the string or buffer is longer than the line in the document then this will raise an error. Dynamic reassignment of sizes

• ls(callback) Returns all keys found in the document. Remember, keys are assumed to be the first string in the beginning of each line in the document.

• close(callback) Closes the file.

Installation

$ npm install random-line-access

License

MIT